Acquired resistance and poor tumor response to epidermal growth factor receptor (EGFR) inhibitors is a significant challenge for effective treatment of head and neck squamous cell carcinoma (HNSCC). Therefore, further identification and characterization of molecular mechanisms associated with HNSCC tumor response to EGFR inhibition could lead to improvements in drug efficacy and HNSCC patient survival. Interleukin-6 (IL-6) production has been shown to promote tumor progression and invasiveness in HNSCC. However little is known about the effect of EGFR inhibitors (EGFRIs) on IL-6 production. The candidate has observed a profound increase in toll-like receptor (TLR) and IL-6 signaling in HNSCC cells resistant to the EGFRI erlotinib compared to erlotinib-sensitive HNSCC cells. These observations led the candidate to the proposal that chronic EGFRI treatment may induce the production and secretion of IL-6 in HNSCC tumor cells via TLR activation, leading to reduced drug efficacy, tumor progression and acquired resistance to EGFRIs. Additionally, prior work in our laboratory has found that EGFR pathway inhibition induced hydrogen peroxide production via activation of NADPH oxidase 4 (NOX4), which has been reported to increase IL-6 expression. Given these observations, EGFRIs may stimulate pathways involving TLRs, NOX4 and IL-6, leading to an inflammatory response in HNSCC tumor cells. The current proposal tests the hypothesis that the antitumor effects of EGFRIs are reduced in HNSCC via NOX4-mediated oxidative stress and TLR-mediated activation of IL-6 signaling in vitro and in vivo. Aim 1 will examine the role of NOX4-mediated oxidative stress in the mechanism of action of EGFRIs in HNSCC in vitro; Aim 2 will determine the contribution of TLR signaling in the mechanism of action of EGFRIs in HNSCC in vitro and in vivo; and Aim 3 will determine if IL-6 pathway blockade would enhance the efficacy of EGFRIs in HNSCC tumor cells in vitro and in vivo. The candidate expects that the successful completion of this application will highlight the significance of TLR, NOX4 and IL-6-mediated inflammation in EGFR-based chemotherapy and contribute in a meaningful way to a new biochemical rationale for the use of IL-6 pathway inhibitors in combination with EGFRIs for the treatment of HNSCC.